The following discussion of traction fluids is taken from U.S. Pat. No. 3,975,278.
"Traction is broadly defined as the adhesive friction of a body on the surface on which it moves. A tractive drive is a device in which torque is transmitted from an input element to an output element through nominal point or line contact typically with a rolling action by virtue of the traction between the contacting elements.
While tractive elements are commonly spoken of as being in contact, it is generally accepted that a fluid film is provided there between. Almost all tractive drives require fluids to remove heat, to prevent wear at the contact surfaces, and to lubricate bearings and other moving parts associated with the drive. Thus, instead of metal to metal rolling contact there is a film of fluid introduced into the load zone. The nature of this fluid determines to a large extent the limits of performance and the capability of the drive.
Many compositions have been suggested as tractive fluids, or tractants, for use in tractive drives with varying degrees of success. Some of these fluids are very efficient and effective tractants, but because of their relatively high cost have been restricted to specialty applications such as constant speed drives for aircraft generators. Other compositions are found to be unsuitable for low temperature operation due to high viscosity or a tendency to crystalize at temperatures of -20.degree. F. or higher. In general, the tractive fluids heretofore have been expensive materials of limited application which required multicomponent blending and the use of additives in order to formulate compositions suitable for general use. For large volume utility applications, such as industrial drives and heavy duty vehicular drives for trucks and buses, less expensive fluids having a wide operable temperature range are sought."
I have found that the product obtained by hydrogenation of a hydrocarbon fraction containing at least 40 weight percent diphenylalkanes, containing 22 to 34 carbon atoms, has properties which make it useful as a traction fluid.